1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming apparatus control method, and a storage medium storing an image forming apparatus control program to detect a full tray state of discharged sheets for the image forming apparatus while saving space and reducing cost of the image forming apparatus.
2. Description of the Background Art
When image forming apparatuses such as printers, copiers, and multi-functional image forming apparatuses print images on sheets of recording media such as paper, the printed sheets are discharged onto a discharge tray from a sheet discharge port and stacked on the discharge tray until a user retrieves the printed sheets from the discharge tray. Typically, the discharge tray is disposed below the sheet discharge port on the housing of the image forming apparatus, and has a given capacity. The sheet stacking capacity defines a limit on the number of sheets that can be stacked on the discharge tray without causing a problem of sheet discharge from the sheet discharge port. Specifically, if too many sheets are stacked on the discharge tray (i.e., if the sheet stacking capacity is exceeded), the stacked sheets may block the sheet discharge port, preventing the sheets from being discharged from the sheet discharge port and possibly causing sheet jamming at the sheet discharge port.
To prevent such sheet jamming, conventional configurations include a detector to detect a stacking condition of sheets on the discharge tray around the sheet discharge port, in which the detector detects whether the stacked sheets have reached a preset full sheet position. When the detector detects that the discharge tray is full, the printing operation is stopped temporarily.
However, the detector employs a physical mechanism such as a moving member and a sensor to detect movement of the moving member. Therefore, a space for the detector is required, incurring production and installation costs. As a result, if the detector is attached to a compact (i.e., slim) and cost-reduced image forming apparatus, both the bulk and cost of the apparatus increases.
JP-2003-192225-A employs a configuration having a filler that moves when sheets are discharged thereon, and a sensor to detect a position of the filler. Specifically, the filler can be moved to a lowest position depending on an amount of sheets on the discharge tray, and the sensor detects such position change of the filler. The position change of the filler is used both for detecting discharged sheets and detecting that the discharge tray is full.
The configuration described in JP-2003-192225-A has the advantage that it uses a single sensor to detect both the discharged-sheets and that the discharge tray is full, thus reducing both the space required for installing the sensor and the installation cost of the sensor. However, detection of both the discharged sheets and that the discharge tray is full increases the size of the filler, thus limiting the extent to which the space for installing the sensor and the installation cost can be reduced.